Conventional water heating systems used in houses and buildings provide hot water to people at a variety of temperatures. Water temperatures ranging from 120 to 140 degrees Fahrenheit are common but can be irritating or even painful if a person remains in contact with the hot water for too long. Water temperatures up to 160 degrees Fahrenheit and higher can scald on contact.
A common method used by people to check the water temperature is to place a hand or finger into the flowing water. Such a check may be harmful if the water is very hot. Another common method is to start a faucet flowing with only cold water then increase an amount of hot water with one hand while testing the water temperature with the other hand. The process is usually time consuming and still presents a possible danger of scalding if the hot water flow is increased too fast.